Effects Of The Planting Of February Orchid(orychophragmus Violaceus L.)on Fates Of Nitrogen In Cotton Field And Cotton Yield

In recent years,cover crops have been widely used in agriculture due to their low planting cost,reduced nutrient loss in winter fallow fields and their abilities to provide nutrients for the growth of major crops in later period.In this study,the experiment was conducted in field conditions,and two cropping systems were set up for the experiment:single cropping of cotton?SC?and the incorporation of February orchid in cotton fields?FO?,and four nitrogen application rates?pure nitrogen?of 0?N0?,112.5?N1?,168.75?N2?and 225?N3?kg/hm² were set in each cropping system.Among them,SC+N3is the conventional production mode of cotton area in the Yellow River basin.Through the study of the four main ways of nitrogen loss in cotton fields?ammonia volatilization,nitrification and denitrification of nitrogen loss,nitrogen leaching and plant nitrogen absorption?,to explore the fates of nitrogen in cotton fields and cotton yields of the planting of February orchid.Impact,so as to explore a cotton planting system that can solve the problem of cotton winter fallow fields,reduce the use of chemical fertilizers,and achieve low-carbon,high-yield and sustainable cultivation goals.The main results were as follows:1.Total ammonia volatilization and N₂O cumulative emissions from cotton fields decreased with the decrease of nitrogen application rate,and the differences generally reached significant levels?P<0.05?.Under the same nitrogen application rate,the total ammonia volatilization and N₂O cumulative emissions of cotton fields with FO were higher than those of SC.Among them,the difference of N₂O cumulative emissions reached a significant level?P<0.05?.2.The soil nitrate nitrogen?NO₃^--N?content showed a time-varying characteristic of high in the early and middle periods,low in the later period of cotton growth and development.With the development of the growing period,the soil NO₃^--N content showed the highest spatial variation in the0?20 cm soil layer and the increase in the 40-60 cm soil layer.The content of soil NO₃^--N accumulation in 0?100 cm soil decreased with the decrease of nitrogen application rate,and the difference generally reached a significant level?P<0.05?.Under the same nitrogen application rate,FO generally increased soil NO₃^--N accumulation in 0?100 cm soil.The incorporation of February orchid in winter cotton field could reduce soil NO₃^--N accumulation in 0?100 cm soil.3.There was no significant difference in the biomass and nitrogen uptake of the treated cotton plants in the early stage of cotton growth and development,but there was a significant difference in the middle and late stage of cotton growth.Obviously,and reducing the rate of nitrogen application,the biomass and nitrogen absorption of cotton plants decreased.Under the same nitrogen application rate,the biomass and nitrogen uptake of cotton plants under FO were higher than those of SC.4.The seed contton yields and lint yields decreased with the decrease of nitrogen application rate,and the differences generally reached a significant level?P<0.05?.Under the same nitrogen application rate,compared with SC,FO increased the seed cotton yield and the lint yield.5.Compared with SC+N3,the total ammonia volatilization of FO+N2 in 2018 and 2019 decreased significantly by 1.24 and 0.85 kg/hm²,respectively,with a decrease of 13.2%and 11.1%;the cumulative N₂O emissions decreased by 0.27 and 0.41 kg/hm²,respectively,with a decrease of 20.5%and 26.5%;the soil NO₃^--N accumulation of FO+N2 in the 0?100 cm soil increased significantly by60.09 kg/hm² during the cotton boll-opening stage,an increase of 19.6%,which was slightly higher than SC+N3 during the harvesting stage.In the middle and late stages of cotton growth and development,the biomass of cotton plants with FO+N2 was significantly higher than or equivalent to SC+N3.Compared with SC+N3,in 9-06?2018?and 9-04?2019?,the nitrogen uptake of FO+N2 increased significantly by8.4%and 7.9%,respectively;the seed cotton yield and lint yield of FO+N2 increased by 68.87 and28.78 kg/hm² respectively in 2018,by 2.1%and 2.5%,and increased by 31.94 and 33.94 kg/hm² in2019,respectively,and the increase rates were 0.7%and 2.2%,respectively.